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Problem DescriptionQ) How to identify services out of requirements – How to guide the reasoning to identify candidate services out of requirements – What modeling methods can help such analysis

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Italian restaurant analogy:Understanding Basic Concepts – Restaurant provides food: a service – After the order is taken, food is produced, served, …: service may consist of other services (service composition) – The menu indicates the service provided: a service description (contract) – The order is written down, or yelled at the cook: services communicate through messages

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Terminology /1 Conceptual service – service that is not yet implemented (implementation agnostic), can be either a software service or not Service candidate – conceptual service identified during analysis and candidate for design Service operation candidate – a service operation identified from functional requirements; it might become a service candidate itself, or be composed (i.e. aggregated) in a (more complex) service candidate Business service – is an (ideally) self-contained, stateless business function that accepts one or more requests and returns one or more responses through a well-defined, standard interface. – During service identification, the elicited business services become the service candidates of the design phase. They might be service operation candidates.

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Service Oriented (SO) analysis  The process of determining how Service oriented business requirements can be analysis represented through services  The process of modeling a service inventory and/or reusing Service oriented it to compose a service oriented design application

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Steps of SO analysis1. Identify business services and service operation candidates – from the target business domain: this can be the list of functional requirements (top-down development) or directly the list of provided business functions – from functional models of pre-existing systems (SO migration)2. Model service candidates – aggregate service operation candidates into service candidates - to do so, recognize overlaps (see next slides) UML activity diagrams (behavior), UML use case diagrams (decomposition); UML class diagrams (data)

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Steps of SO analysisA) gluing service operations to define self-contained business logic Service operation Service candidates candidates (self-contained)

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Service modeling guidelinesB) reusability of common business logic across different processes  Task service candidates – reusability of common business logic across different processes

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Service modeling guidelines Task service candidates – reusability of common business logic within a process

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Model service candidates: businessprocess logic Not service operation candidates (from the Order Fulfillment Process example): – if PO document is valid, proceed with the step “transform PO document” – if the PO document is invalid, “end process” This belongs to the respective task services

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Summary of Service IdentificationMethod Step 1: Business service identification. – The business services are elicited by means of business process models and conceptual data models. – These two models can be determined either from functional models of pre-existing systems (i.e. bottom-up SOA migration), or from the target business domain, as the list of functional requirements (i.e. top-down service development). – Conceptual data models, instead, facilitate identification of the business services addressing the functionality of business entities Step 2: Business service decomposition. – Given the identified business services, this step elicits the candidate services and their constituent service operations.